Ultra high frequency amplifier



APril 1947. s. G. TOMLIN 2,419,800

ULTRA HIGH FREQUENCY AMPLIFIER Filed June 2, 1942 rman/5;

Patented Apr. 29, 1947 UNITED STATES PATENT OFFICE ULTRA EHGH FREQUENCY AMPLIFIER Stanley Gordon Tomlin, London W. C. 2, England, assignor to Standard Telephones and Cables Limited, London, England, a British company Application June 2, 1942, Serial No. 445,508 In Great Britain May 10, 1941 1 Claim.

The present invention relates to ultra high frequency amplifiers and particularly though not solely to ultra hi h frequency amplifiers associated with circuit arrangements utilis ng concentric line conductors.

According to the invention an amplifier for ultra high frequencies comprises an input and an output resonant chamber arranged in alignment with each other and each containing a part of a h rmionic lectr n i char e evice c mlar to the axis of the chambers. The outer conprising at least a cathode, an anode and a control ductors 2, 2' are provided at the adjacent ends grid, said cathode being electrically connected to with fl n e 3 m respectively and which are the input chamber and the anode being electriparahel to each other, The control grid is cally connected to the output chamber and said vided t an nnular plate member ll integral Control grid being p id With n allXilia-ly 5 therewith and preferably of copper. This anmetallic member extending outside the enclosing nuler plate member H is located between the envelope of the discharge device and sandwiched two flanges m m so as to f therewith between the walls of the two chambers to form a Capacitive eouphngs The central conductor 3 Screen between the input and output Circuits! is shown as a hollow conductor serving as one blocking capacities being inserted in the grid lead for the cathode heater, the other lead being cathode path and in the grid-anode path. The a conductor Within 3 as Shown blocking capacities enable direct current poten' The input feed circuit is shown as a concentric tials to be the Fespective electrodes line l2, l3, the outer conductor l2 of which is carrymg the mventlon into prajctlce both slidably connected to the outer conductor or wall Sald Phambers may t: settlon of t of chamber 2 and the inner conductor l3 thereof ceintnc cottductor tta'nsmlsslon hne provlded is slidably connected to the inner conductor or Wlth an adwst'ame plston to tunethe chambers wall of chamber 2. The slidable connections are to the frequency of operation. In an alternative to give an adjustable coupling The output cirarmngement elther or both chambers may cult is shown also as a concentric transmission prise disc resonators provided with suitable line having outer conductor M and inner com tuning arrangements, as hereinafter described. ducter |5 The nductor M is a push fit in the The former arrangement is particularly useful piston may be rotated Conductor sis for use with concentric conductor transmission looped and one end of the loop is connected to I 4 hne systems. so that the loop may be rotated, thus providing The blocking capacities may be conveniently an adjustable out ut cou ling formed between the auxiliary metallic member of In the arranggment s in Figure 3 a the grid the walls of the input and output hollow d sc resonator is used for the output chambers, or in any other convenient part of the circuit Wimst the in ut rcuit is the me grid-cathode and grid-anode circuits. In this Th di p i latter case the rid is directly connected to the 40 i 8 SC 9 or is m t 8 i walls of the chambers and earthed for both high i {apamtatlve connectmn the frequency and direct currents. In the former f t 9 Ve as 9 the output molucmr case the grid is earthed as regards the high 2 of Flgtlre t gnd 1 of the valve as m the frequency currente case of Figure is mounted on an annular copper The invention 1 be better understood fro 4.5 d1sc ll sealed into the glass envelope, and which the followin description taken in o jun tio 'proJects outside the envelope 9 to cooperate with with the accompanying drawings, in which; the flange on the outer conductor '2 of the input Fig, 1 sh ws one form of th amplifier emb0dy circuit to form a capacitive coupling. The second ing th i ti nd, copper disc I6 is also sealed into the glass en- Fig. 2 is an explanatory diagram. velope of the valve and acts as a closure for the Fig. 3 shows an alternative form of output outer end thereof. This second disc or outer fiat circuit. wall of the resonator, which is disposed parallel Fig. 3A is a modification of Fig. 3. to the first-mentioned disc, has the anode 8 In Fig. 1 the two chambers are indicated at I mounted thereon, and the disc resonator DR is and I, each comprising sections of concentric built upon the two discs H and I6, one fiat wall of the resonator being capacitivcly coupled to the copper disc II.

The resonator is tuned to the working frequency by screwing plugs of metal or dielectric substance into the resonant chamber, or alternatively by making adjustable as, by corrugating the copper disc 16 carrying the anode 8 so that the anode can be moved slightly towards or away from the grid, thus varying the anodegrid capacity which loads the resonator.

The output from the resonator is taken by means of concentric conductors I4, l5, the inner conductor being connected to the outer con-,

ductor M by a loop to form an inductive coupling with the resonator. The conductor 14 is a push fit in the fiat end wall of the resonator so as to be rotatable to form an adjustable output coupling.

The advantages of this system are:

(a) The excellent screening of the output from the input circuit and consequent elimination of positive feedback. The only possible source of feedback is the anode-cathode capacity which can be kept extremely low.

(1)) The negative feedback inherent in this circuit ensures complete stability and brings all its other advantages. The existence of this feedback is more evident from the equivalent circuit of Fig. 2. The anode current flows through the input impedance Zg. The input is represented at c.

There is no impedance common to the output and input circuits.

The power or voltage gain from this system can be shown to be:

should be properly terminated.

The triode is of special design with small cathode-grid spacing to minimise transmit time effects, and has a very fine grid so that the ampli- 'fication factor may be as large as possible. With a a of the order of 100 it should be possible to obtain power amplification of 30 times with a bandwidth of 4 mc./s. at a wavelength of 50 cms.

This amplification arrangement overcomes the difiiculties due to instability at ultra high frequencies by:

(i) Completely shielding the output from the input circuit.

(ii) Eliminating impedances common to the output and input circuits.

(iii) Reducing the anode cathode capacity to negligible proportions.

(iv) Taking advantage of the properties of negative feedback.

. Whilst particular types of connections have been shown on the input and output sides of the amplifier, both types may be used on either side. Furthermore, the coupling between the input and output transmission line and the respective chambers may be made in any other known manner, for instance by capacitive coupling.

What is claimed is:

An amplifier for ultra high frequency comprising input and output resonator chambers at least one chamber consisting of a concentric conductor line section, said chambers being arranged in concentric alignment with each other and each enclosing a portion of an electron discharge device which comprises at least an anode, a cathode and a control grid, said cathode being electrically connected to the input chamber, said control grid having an annular metallic portion extending beyond the enclosing envelopes of the discharge device and sandwiched between the opposed end Walls of said two chambers to form an accessible screen'between the input and output circuits, blocking capacities inserted in the grid cathode path and in the grid-anode path, at

least one of said resonator chambers together STANLEY GORDON TOMLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,153,728 Southworth Apr. 11, 1939 2,034,433 Heintz Mar. 17, 1936 2,052,888 Lindenblad Sept. 1, 1936 2,253,489 Southworth Aug. 26, 1941 2,284,405 McArthur May 26, 1942 2,169,396 Samuel Aug. 15, 1939 2,278,210 Morton Mar. 31, 1942 2,283,895 Mouromtsefi, et al. May 19, 1942 

